1. Field of the Invention
This invention relates generally to the field of fire and explosion sensing and suppression systems, and more particularly to those systems that suppress fires and explosions but discriminate against various types of radiation that may resemble fires or explosions.
2. Description of the Prior Art
Systems for sensing and suppressing fires and explosions are generally known. Some prior art systems have employed two detectors, each detector detecting radiation within different spectral bandwidths. An example of such a system is disclosed in U.S. Pat. No. 3,931,521 to R. J. Cinzori and assigned to the assignee herein. The dual-channel system taught by U.S. Pat. No. 3,931,521 utilizes dual detectors and generates an output signal when both channels detect radiation of a predetermined threshold intensity.
Fire sensor systems must be highly reliable and capable of discriminating against many different types of stimuli that resemble fires and explosions. An example of a successful discriminating fire sensor system is disclosed in U.S. Pat. No. 3,825,754 to R. J. Cinzori, et al. That fire sensor system discriminates against, among other things, the explosion of a round of ammunition which does not subsequently cause a fire.
Another successful discriminating fire sensor system is disclosed in our pending application Ser. No. 269,208, now abandoned, filed June 2, 1981. That sensor system utilizes a third channel to discriminate, among other things, between hydrocarbon fires and the flash caused by a projectile piercing the wall of a monitored area. The decay of the flash is electrically simulated by the system by inhibiting an output signal for a period of time before allowing the system to sense whether a fire has developed after the effects of the flash substantially subside. The disclosures of U.S. Pat. Nos. 3,931,521 and 3,825,754 are incorporated herein by reference.
When a projectile penetrates the wall of a monitored area, the resulting flash effects may persist for a relatively long time (50 milliseconds or more). If no fire results from the projectile penetration, the fire sensor system must not cause the release of suppressant. However, if the penetrating round ignites fuel, a fire can rapidly grow to magnitudes larger than the capacity of the suppressant; the fire sensor system must respond while the growing fire is still manageable. Prior art fire sensor systems are not fully able to handle both long flash decays and the possibility of a rapid fire buildup, and the present invention is directed to the solution of this problem.